1. Field of the Invention
The present invention relates to a monolithic ink-jet printhead and a method of manufacturing the same, and more particularly, to a monolithic ink-jet printhead in which an ink chamber and a nozzle are effectively and easily formed, and a method of manufacturing the same.
2. Description of the Related Art
In general, ink-jet printheads eject ink droplets using an electro-thermal transducer (ink-jet type), which generates bubbles in ink using a heat source.
FIG. 1 is a schematic perspective view illustrating a structure of a conventional ink-jet printhead, and FIG. 2 is a schematic cross-sectional view of the ink-jet printhead shown in FIG. 1. Referring to FIGS. 1 and 2, the ink-jet printhead includes a manifold (not shown) to which ink is supplied, a substrate 1 on which a heater 12 and a passivation layer 11 protecting the heater 12 are formed, a passage plate 2 which includes an ink passage 22 and an ink chamber 21 formed on the substrate 1, and a nozzle plate 3 which is formed on the passage plate 2 and has an orifice 31 corresponding to the ink chamber 21.
In general, the passage plate 2 and the nozzle plate 3 are formed by a photolithography process using polyimide. In the conventional ink-jet printhead, the passage plate 2 and the nozzle plate 3 are formed of the same material, for example, the polyimide. The nozzle plate 3 may be easily detached from the passage plate 2 due to a weak adhering property of the polyimide.
In order to solve this problem, in a conventional method of manufacturing the ink-jet printhead, when the passage plate 2 and the nozzle plate 3 are formed of the polyimide as separate layers as described above, the passage plate 2 and the nozzle plate 3 are separately formed from the substrate 1 and are bonded on the substrate 1. In this method, due to several problems including a structural misalignment, the nozzle plate 3 cannot be attached to the substrate, such as a wafer, and the nozzle plate 3 should be attached to each chip which is separated from the wafer. Thus, this method results in low productivity.
Meanwhile, in conventional methods of manufacturing an ink-jet printhead disclosed in U.S. Pat. Nos. 5,524,784 and 6,022,482, a mold layer is used as a sacrificial layer so as to form an ink chamber and an ink passage.
In the conventional methods, the sacrificial layer is formed of a photoresist on a substrate to correspond to patterns of the ink chamber and the ink passage, polyimide is coated to a predetermined thickness on the sacrificial layer, and a passage plate and a nozzle plate are formed as a single body. Then, an orifice (nozzle) is formed in the nozzle plate, and the sacrificial layer is finally removed such that the ink chamber and the ink passage are formed below the nozzle plate. In the conventional methods of forming the ink passage and the orifice (nozzle) using the mold layer, the passage plate and the nozzle plate are formed of the polyimide to protect the mold layer. However, they cannot be hard-baked at a sufficient temperature since the mold layer is formed of the photoresist having a low heat-resistant property. As far as the mold layer exists, the passage plate or the nozzle plate formed of the polyimide cannot be hard-baked. Likewise, the non-hard-baked passage plate or nozzle plate is damaged by an etchant when the mold layer used to form the ink passage and the ink chamber is removed. In particular, a portion where the passage plate contacts the nozzle plate is etched, and an interface between the passage plate and the nozzle plate are damaged by the etchant and become unstable, thereby getting loose from the substrate.